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Organic Electroluminescent Device And Manufacturing Method Therefor - Patent 6853130


1. Field of InventionThe present invention relates to organic electroluminescent devices, which are electrical device light emitting devices used for displays, light sources for displays, and the like, and to manufacturing methods therefor.2. Description of Related ArtRecently, as self-luminous displays replace liquid crystal displays, development has been advancing rapidly of light-emitting devices (organic electroluminescent devices, hereinafter referred to as "organic EL devices"), which have a structure inwhich a light-emitting layer formed of an organic material is provided between an anode and a cathode. Among these, a high-transmission EL device, a so-called transparent EL device (TOELD) used in the visible light region, which can emit light from thetwo electrode sides, has been desired, since overlapped displays can be performed by disposing another display device thereunder. A particular structure of this device is disclosed in, for example, Appl. Phys. Lett. 68(19), 6 May 1996, p 2606. Inthis publication, it is disclosed that an aluminum complex Alq3, which is a low molecular material, is used as a light-emitting layer, a cathode is formed by co-deposition of Mg and Ag, an ITO film is formed by sputtering thereon for sealing or forassistance to the cathode so as to form a device, and a threshold voltage of approximately 8 V is achieved. In the structure described above, in view of the life and the threshold characteristics of a material used for the light-emitting layer, Mg andAg are used for the cathode, and in addition, ITO is used for the upper layer thereon.Concerning organic EL devices, a light-emitting material having a low threshold value can be used for a light-emitting layer, and a metal material having a low work function can be used for a cathode so as to realize operation at a low thresholdvoltage. However, in the structure proposed in the paper described above, Mg and Ag are not sufficient in view of the work functions, and since ITO

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